Delta Air Lines misled customers with its sustainability claims, a new class action lawsuit alleges. The suit was filed in California yesterday and seeks damages for any resident who’s been on a Delta flight since it made a big climate commitment back in 2020.

That year, the company made a $1 billion pledge to become carbon neutral. Instead of slashing its emissions entirely, the plan relied on carbon credits to offset the airline’s pollution. The credits are supposed to represent tons of carbon dioxide emissions either prevented or taken out of the atmosphere. But the math on carbon offsets hasn’t added up. Years of academic research and investigations have shown that carbon offsets often fail to represent real reductions in greenhouse gas pollution.

The plaintiff, Nickelodeon writer Mayanna Berrin, says in the suit that she “paid a substantial price premium due to the false and misleading carbon neutral claim.” “I felt comfortable paying more because I was neutralizing when I needed to travel for work or to see my family,” Berrin told The Associated Press. Had she known that the company’s carbon neutral claims were “false and misleading,” she wouldn’t have paid extra to fly with Delta, the complaint says.

The aviation industry has come under fire for the way it uses carbon offsets to sell supposedly more sustainable flights. An October 2022 report found that some of Europe’s biggest airlines purchased offsets from highly suspect forestry projects. The projects capitalize on the ability of trees to store CO2, but that benefit is temporary unless the projects save forests from logging and fires for hundreds of years.

Delta relied on embattled carbon credit broker Verra to verify its forestry offsets in 2021, according to the new lawsuit. A Guardian investigation in January found that more than 90 percent of rainforest carbon offsets certified by Verra are likely “phantom credits” that don’t represent any real reductions in emissions.

Delta was one of the early airlines to commit to becoming carbon neutral, but it included few details at the time about how it would follow through on its “10-year commitment to mitigate all emissions from March 2020 forward.” Since then, the company has had to grapple with the stark reality that carbon offsets have a terrible track record and now plans to reach net-zero carbon dioxide emissions by 2050.

In an email to The Verge, Delta claims that since March 2022, it has “fully transitioned its focus away from carbon offsets toward decarbonization of our operations, focusing our efforts on investing in sustainable aviation fuel, renewing our fleet for more fuel-efficient aircraft and implementing operational efficiencies.” The class action lawsuit is “without legal merit,” the email says.

Delta was responsible for the equivalent of roughly 43.2 million metric tons of carbon dioxide emissions in 2022, according to its latest ESG report. That’s comparable to the climate pollution from 109 gas-fired power plants in a year.